class Container {
  static of(value) {
      return new Container(value)
  }
  constructor(value) {
      this._value = value
  }
  map(fn) {
      return Container.of(fn(this._value))
  }
}
class Maybe {
  static of(value) {
      return new Maybe(value)
  }
  
  constructor(value) {
      this._value = value
  }

  isNothing() {
      return this._value === null || this._value === undefined
  }

  map(fn) {
      return this.isNothing() ? this : Maybe.of(fn(this._value))
  }
}

module.exports = {Maybe, Container}